Apparatus for and method of improving efficiency of transceivers in radio products

ABSTRACT

A system and method for minimizing power dissipation in a battery-operated mobile unit by adaptively controlling a voltage converter to provide a variable power supply voltage to a transmitter. In the preferred embodiment, the voltage converter is coupled to receive a source voltage from a battery, and is coupled to provide operating power to the transmitter or the power amplifier. The voltage converter is also coupled to receive a control signal from a controller, which adaptively activates the voltage converter to transform the source voltage to a converted voltage, or deactivates the voltage converter so as to directly apply the source voltage to the transmitter. Power dissipation is therefore minimized when conversion functions of the voltage converter are deactivated when voltage conversion is unnecessary.

FIELD OF THE INVENTION

The present invention relates to transceivers in radio products. Morespecifically, the present invention relates to an apparatus for andmethod of improving efficiency in battery-operated portabletransceivers.

BACKGROUND OF THE INVENTION

Portable battery-powered radio products, such as cellular phones, arebecoming increasingly compact as a result of the development of smallerand longer-lasting batteries. These batteries, however, typically do nothave high output voltages. For instance, lithium batteries, commonlyused in many cellular phone products, have an output voltage around 3.6volts per cell. Such an output voltage, while useful in manyapplications, may not be sufficient for power amplifiers which typicallyrequire a higher supply voltage for optimum performance. Furthermore,different components within the portable radio products may requiredifferent power supply voltages for optimal performance. Thus, a voltageconverter is often used to transform the battery voltage to othervoltages as required by the specific applications.

One major drawback of using a voltage converter in portable radioproducts, however, is power dissipation. The problem is exacerbated inportable or mobile radio products where battery capacity is limited.Thus, even a low level of dissipation by the voltage converter causes asignificant decrease in battery life. In order to decrease powerdissipation, switching voltage regulators are typically used as voltageconverters. A switching voltage regulator is well known in the art andgenerally comprises a pass transistor which oscillates between cutoffand saturation. Thus, the pass transistor acts as a switch that israpidly being turned on and off. The rapid switching, coupled with anetwork of inductors and capacitors, boosts up or bucks down an inputvoltage. A text-book example of such a switching voltage regulator canbe found in Greenfield, J., Practical Transistors and Linear IntegratedCircuits, pp. 505-515, John Wiley & Sons, Inc., 1988.

In order to further minimize power dissipation, highly complicatedvoltage regulators using state of the art components and designs havebeen devised. However, the level of dissipation remains relatively high.Indeed, in prior art battery-operated portable transceivers, the maximumoverall transmitter power efficiency is limited to roughly 40% when thetransmitter transmits at its maximum output power. A significant amountof energy is consumed by the switching voltage regulator. When thetransmitter transmits at lower power levels, the overall transmitterpower efficiency becomes even lower. Thus, what is needed is anapparatus for and method of increasing the efficiency of the voltageconverters such that a minimum amount of energy is dissipated in thevoltage converters. What is further needed is an apparatus for andmethod of adaptively controlling power supplied to power amplifiers andsignal transmitters in battery-operated transceivers to achieve maximumefficiency.

Accordingly, the present invention provides a system for and method ofminimizing power dissipation of voltage converters in radio products.The present invention also provides a mechanism for providing theminimum necessary power to the transceiver by adaptively providing ahigh power supply voltage and a low power supply voltage to thetransceiver. Further, the present invention provides a mechanism andmethod for controlling a switching voltage regulator to supply a lowpower supply voltage at maximum efficiency. These and other advantagesof the present invention not specifically mentioned above will becomeclear within discussions of the present invention presented herein.

SUMMARY OF THE INVENTION

A system and method are described herein for minimizing powerdissipation and power supplied to a transmitter or a power amplifier ina battery-operated mobile unit by adaptively controlling a voltageconverter to provide a variable power supply voltage to the transmitteror power amplifier. In the preferred embodiment, the voltage converteris coupled to receive a source voltage from a battery, and is coupled toprovide operating power to the transmitter or power amplifier. Thevoltage converter is also coupled to receive a control signal from acontroller, which adaptively activates the voltage converter totransform the source voltage to a converted voltage, or deactivates thevoltage converter to directly apply the source voltage to the poweramplifier. Power dissipation is therefore minimized when conversionfunctions of the voltage converter are deactivated when voltageconversion is unnecessary.

In order to adaptively activate and deactivate conversion functions ofthe voltage converter, an appropriate supply voltage required for eachpossible transmitter output level is pre-determined. Then, during theoperation of the transmitter and according to the required transmitteroutput level, an appropriate supply voltage to the transmitter isdetermined and compared to the source voltage. If the appropriate supplyvoltage is substantially equivalent to the source voltage, voltageconversion functions of the voltage converter are deactivated. As aresult, the source voltage will be applied directly to the transmitterwithout significant dissipation. Whereas, if the appropriate supplyvoltage is higher than the source voltage, voltage conversion functionsof the voltage converter are activated, causing the source voltage to betransformed to an up-converted voltage, which is then applied to thetransmitter.

In furtherance of the preferred embodiment of the present invention, thevoltage converter may include a switching voltage regulator fortransforming the source voltage to an up-converted voltage. Thecontroller may comprise a digital signal processor (DSP),microcontroller, or other types of microprocessor for providing anoscillating pulse to control the operation of the voltage regulator. Inaddition, the controller may control a duty-cycle of the oscillatingpulse, which in turn controls a voltage gain of the voltage regulator. Atransmitter-amplifier is coupled to an output of the voltage regulatorfor receiving a power supply voltage. In the preferred embodiment, thepower supply voltage is chosen to achieve maximum efficiency for a givensignal power to be put out by the transmitter-amplifier.

In an alternate embodiment of the present invention, the mobile unit mayinclude a battery having a high source voltage, a voltage regulator fordown-converting the source voltage, and a signal transmitter or poweramplifier coupled to receive the source voltage or a down-convertedvoltage from the voltage regulator. The mobile unit may also utilize acontroller for providing an oscillating pulse to control the operationof the voltage regulator. When a high transmitter output level isnecessary to transmit signals from the mobile unit to a base station,the controller deactivates the voltage conversion functions of thevoltage regulator in order to directly apply the source voltage to thesignal transmitter or the power amplifier. When a low transmitter outputlevel is appropriate, the controller activates the conversion functionsof the voltage regulator such that the down-converted voltage is appliedto the signal transmitter or the power amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of the preferred embodiment of thepresent invention.

FIG. 2 is a flow diagram illustrating the method according to thepreferred embodiment of the present invention.

FIG. 3 illustrates a schematic of the preferred embodiment of thepresent invention.

FIG. 4 illustrates a schematic of an alternate embodiment of the presentinvention.

FIG. 5 is a flow diagram illustrating the method according to thealternate embodiment of the present invention as shown in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description of the present invention, a systemfor and a method of minimizing power loss in a battery-operated mobileunit of a transceiver system, numerous specific details are set forth inorder to provide a thorough understanding of the present invention.However, it will be recognized by one skilled in the art that thepresent invention may be practiced without these specific details orwith equivalents thereof. In other instances, well known methods,procedures, components, and circuits have not been described in detailas to avoid unnecessarily obscuring aspects of the present invention.

In the following, the present invention is discussed in relation to GSM(Global System for Mobile Communication) type transceiver systems. TheGSM system is well known in the art and is fully described in Mouly, M.,and Pautet, M., The GSM System for Mobile Communications, published bythe authors, 1992, which is incorporated herein by reference. However,it should be apparent to those ordinarily skilled in the art that thepresent invention and principles described herein may be applied toother types of transceiver systems as well.

In GSM transceiver systems (mobile stations), the highest transmitteroutput level is about +33 dbm. The lowest transmitter output level isabout +5 dbm. The low output level is typically used when a weak signalis sufficient for transmitting data between a mobile unit and a basestation of the system. Further, in GSM systems, the appropriatetransmitter power level or output level is determined by a base station,and is communicated to a mobile unit, which adjusts its transmitteroutput level accordingly. The apparatuses and circuitry for determiningthe distance between the mobile unit and the base station, andalgorithms for calculating an appropriate transmitter output level arewell known in the art. Thus, the detail of such apparatuses andcircuitry are not discussed here so as to avoid unnecessarily obscuringthe features of the present invention.

FIG. 1 illustrates a block diagram of the preferred embodiment of thepresent invention. As shown, a mobile unit 10 according to the presentinvention comprises a battery 102 for generating a source voltage, avoltage up-converter 104 coupled to receive the source voltage from thebattery 102, and a transmitter circuit 106 coupled to receive operatingpower from the voltage converter. A controller 108 is also coupled tothe voltage up-converter 104 for adaptively activating and deactivatingconversion functions of the voltage converter 104 according to a LEVEL₋₋SELECT signal. The LEVEL₋₋ SELECT signal may be generated by a basestation (not shown) or by a circuit (not shown) which determines anappropriate transmitter output level of the mobile unit 10. Preferably,the controller 108 is implemented as an application specific integratedcircuit (ASIC). When the conversion functions of the voltage converter104 are activated, an up-converted voltage is applied to the transmittercircuit 106. When the conversion functions of the voltage converter 104are deactivated, the source voltage generated by the battery is directlyapplied to the transmitter circuit 106. As voltage conversion functionsare deactivated when voltage conversion is inappropriate,energy-dissipating conversion processes are completely bypassed. As aconsequence, power loss is minimized.

The operation of the mobile unit 10 is illustrated by the flow diagramin FIG. 2. First, an appropriate transmitter output level for datatransmission between the mobile unit 10 and the base station isdetermined (Box 202). After the appropriate transmitter output level isdetermined, the base station will signal the mobile unit 10 to transmitdata at the appropriate level (Box 204). Alternatively, circuitry withinthe mobile unit 10 may determine the appropriate transmitter outputlevel based on the strength of the signals received from the basestation.

The next step is determining an appropriate supply voltage to thetransmitter circuit 106 such that signals are transmitted with maximumefficiency (Box 206). Preferably, the appropriate supply voltage isdetermined by the controller 108, which also compares the appropriatesupply voltage to the source voltage (Box 207). If it is determined thatthe appropriate supply voltage is substantially equivalent to the sourcevoltage, then a first control signal is sent from the controller 108 tothe voltage converter 104 to deactivate up-conversion functions of thevoltage converter 104 (Box 208). The source voltage will be directlyapplied to the transmitter circuit 106 (Box 210). Consequently, inputsignals to the transmitter circuit 106 will be amplified to theappropriate transmitter output level with maximum efficiency (Box 212).

On the other hand, if it is determined that the appropriate supplyvoltage is higher than the source voltage, then a second control signalis sent to the voltage converter 104 to activate conversion functions ofthe voltage converter 104 (Box 214). The source voltage is thenup-converted by the voltage converter 106 (Box 216), and theup-converted voltage will be applied to the transmitter circuit 104 (Box218). As a result, input signals to the transmitter circuit 106 will beamplified at the appropriate transmitter output level with maximumefficiency (Box 220).

FIG. 3 illustrates a schematic of the preferred embodiment of thepresent invention. It should be understood that the circuit as shown inFIG. 3 is a simplified example of how the preferred embodiment may beimplemented, and therefore, should not be construed as a limitation.Further, it should be apparent to those ordinarily skilled in the art,upon studying this disclosure, that many other implementations arepossible.

As shown in FIG. 3, a mobile unit 300 according to the preferredembodiment includes a battery 302 having an output voltage V_(BATTERY),a voltage up-converter 350 coupled to receive V_(BATTERY) from thebattery 302, a power amplifier 312 coupled to receive supply voltageV_(SUPPLY) from the voltage up-converter 350. The voltage up-converter350 is also coupled to receive oscillating signals OSC and OSC from acontroller 316. More specifically, the voltage up-converter 350comprises an inductor 304 having a first end coupled to the battery 302,and a second end coupled to a source of a first FET transistor 306, andto a source of a second FET transistor 308. A drain of the first FETtransistor 306 is coupled to ground, and a gate of the first FETtransistor 306 is coupled to the controller 316 to receive a firstoscillating pulse OSC. A gate of the second FET transistor 308 is alsocoupled to the controller 316 to receive a second oscillating pulse OSC,which is an inverse of the oscillating pulse OSC. A drain of the FET 308is coupled to a first node of a capacitor 310 to form a voltageregulator output node 320. The node 320 is coupled to supply operatingpower to a power amplifier 312 for amplifying input signal Φ_(in) tooutput signal Φ_(OUT). The voltage regulator output node 320 is alsocoupled to provide a feedback signal to the controller 316. Thecontroller 316 is also configured to receive a LEVEL₋₋ SELECT signalfrom a base station (not shown). Alternatively, the LEVEL₋₋ SELECTsignal may be generated by circuits and components contained within themobile unit 300. Apparatuses and circuits for determining an appropriatetransmitter output level are well known in the art. Therefore, thedetails of such apparatuses and circuits are not discussed here so as toavoid obscuring essential features of the present invention.

In operation, upon receiving the LEVEL₋₋ SELECT signal, the controller316 will determine an appropriate output voltage for the voltageconverter 350. If it is determined that the appropriate output voltageis substantially equivalent to the source voltage V_(BATTERY), thecontroller 316 will stop providing oscillating signals OSC and OSC tothe gates of the transistors 306 and 308. Rather, the controller 316will supply constant voltages to the transistors 306 and 308 todeactivate the conversion functions. In particular, a constant zero voltis applied to the gate of the transistor 306 to operate the transistor306 in a cutoff mode. At the same time, a constant voltage is applied tothe gate of the transistor 308 to operate the transistor 308 in asaturated mode. In saturated mode, the voltage drop across the sourceand drain of the transistor 308 is de minimis. As a result, V_(BATTERY)generated by the battery will be directly applied to the voltageregulator output node 320. Accordingly, the transmitter 312 will besupplied with a low power supply voltage when the voltage regulator 350is "OFF".

However, if it is determined that the appropriate output voltage ishigher than V_(BATTERY), the controller 316 will provide oscillatingsignals OSC and OSC to the transistors 306 and 308. The oscillatingsignals OSC and OSC cause the transistors 306 and 308 to act as switchesthat are rapidly turned on and off. The rapid switching, coupled withthe inductor 304 and capacitor 310, generates an output voltageV_(SUPPLY). The controller 316 is also capable of fine-tuning the outputvoltage of the voltage regulator by adjusting the pulse-width of signalsOSC and OSC. As a consequence, V_(BATTERY) is up-converted to a voltageV_(SUPPLY), which is applied to drive the power amplifier 312. In thepreferred embodiment, V_(SUPPLY) is 4.8 V, which corresponds to anoptimum supply voltage for a typical power amplifier, such as RockwellRF130 GSM PA, commonly used in GSM radio products. In addition, in thepreferred embodiment, V_(BATTERY) is 3.6 V, corresponding to a typicaloutput voltage of a lithium-ion battery cell.

It should be noted that the present invention is not limited toup-converting a low battery voltage to a high voltage. For applicationsusing high voltage batteries, energy will be wasted when a lowtransmitter output level is sufficient for data transmission. In thatcase, voltage down-converters may be used. The present invention is alsoapplicable when using a down-converter to down-convert a high batteryvoltage to a low voltage for low power operations of the transmitter.This alternate embodiment of the present invention is illustrated inFIGS. 4 and 5.

As shown in FIG. 4, a battery 502 is coupled to a source of an FETtransistor 506. A gate of the FET 506 is coupled to receive anoscillating signal OSC from a controller 516. A drain of the FET 506 iscoupled to a cathode of a diode 508. The anode of the diode 508 iscoupled to ground. The cathode of the diode 508 is also coupled to afirst end of an inductor 504. A second end of the inductor 504 iscoupled to a first node of a capacitor 510 to form a voltage regulatoroutput node 520. The node 520 is coupled to supply operating power to apower amplifier 512 for amplifying input signal Φ_(IN) to output signalΦ_(OUT). The voltage regulator output node 520 is also coupled toprovide a feedback signal to the controller 516. The controller 516 isalso coupled to receive a LEVEL₋₋ SELECT signal transmitted by a basestation or generated by other components and circuitry contained withinthe mobile unit 500. The components and circuitry for determining anappropriate transmitter power output level are well known in the art,and are therefore not described here in detail as not to unnecessarilyobscure aspects of the present invention.

FIG. 5 illustrates the operation of the circuit as shown in FIG. 4.First, an appropriate transmitter output level for data transmissionbetween a mobile unit and a base station is determined (Box 602). Then,the mobile unit 500 receives a LEVEL₋₋ SELECT signal representative ofthe appropriate transmitter output level from a base station (Box 604).The controller 516, after receiving the LEVEL₋₋ SELECT signal,determines an appropriate power supply voltage for the power amplifier512 (Box 606). The appropriate power supply voltage is then compared tothe source voltage V_(BATTERY) (Box 608) If the appropriate power supplyvoltage for the power amplifier 512 is substantially equivalent to thesource voltage V_(BATTERY), the controller 516 will stop providingoscillating signal OSC to the transistor 506 (Box 610). Rather, thecontroller 516 will supply a constant voltage to the transistor 506 suchthat conversion functions of the voltage regulator 550 are deactivated.In particular, a constant voltage is applied to the gate of thetransistor 506 to drive the transistor 506 to saturation. As a result,the source voltage V_(BATTERY) will be directly applied to the poweramplifier 512 (Box 612). On the other hand, if the appropriate powersupply voltage is lower than the source voltage V_(BATTERY), thecontroller 516 will provide oscillating signal OSC to the transistor 506(Box 614). Voltage conversion functions of the down-converter isactivated. As a consequence, V_(BATTERY) is down-converted to a lowervoltage Vs.

A system for and method of minimizing power dissipation and powersupplied to a transmitter of a battery-operated mobile unit have thusbeen disclosed. By adjusting the power supply voltage to the poweramplifier to correspond with an appropriate output level, energy issaved. Furthermore, by shutting off conversion functions of voltageconverters in the mobile unit when voltage conversion is not necessary,power dissipation is minimized. As power supplied to transmitters isoptimized and power dissipation is minimized, significant improvement inthe talk-time of portable radio products is achieved. Overall efficiencyof the transceiver is also improved.

What is claimed is:
 1. A system for minimizing power dissipation in abattery-operated mobile transceiver unit, the system comprising:abattery for supplying battery voltage; a converter coupled to thebattery for converting the battery voltage to a supply voltage; atransmitter coupled to the converter for receiving the supply voltage orthe battery voltage; and a controller coupled to the converter fordeactivating the converter when the battery voltage is appropriate fordelivering operating power to the transmitter, the controller comprisinga pulse generator for producing an oscillating pulse to activate theconversion functions of the converter and a constant voltage todeactivate the conversion functions of the converter.
 2. The systemaccording to claim 1 wherein the converted voltage supplies operatingpower to the transmitter when the conversion functions of the converterare activated.
 3. The system according to claim 1 wherein the controlleractivates the conversion functions of the converter when an output levelof the transmitter associated with the battery voltage is inappropriatefor transmitting data from the mobile unit to the base station.
 4. Thesystem according to claim 1 wherein a first supply voltage is 3.6 V. 5.The system according to claim 1 wherein a second supply voltage is 4.8V.
 6. A method of minimizing power supplied to a transmitter of abattery-operated mobile unit by adaptively providing either a supplyvoltage or a source voltage to the transmitter, the method comprisingthe steps of:a) determining transmitter output level for transmittingdata between the mobile unit and a base station; b) determining supplyvoltage needed at the transmitter, based on operating the transmitter atthe determined transmitter output level; c) determining if the neededsupply voltage is substantially the same as a source voltage in themobile unit; d) applying the source voltage to the transmitter if theneeded supply voltage is substantially the same as the source voltage;e) converting the source voltage to the needed supply voltage if theneeded supply is not substantially the same as the source voltage byproviding an oscillating pulse to activate a voltage converter using apulse generator; and f) preventing activation of the converting stepwhen the supply voltage is substantially the same as the source voltageby providing a constant voltage to deactivate the voltage converterusing the pulse generator.
 7. A method of minimizing power supplied to atransmitter of a battery operating mobile unit by adaptively providingvariable supply voltages to the transmitter, the method comprising thesteps of:providing a battery having a battery voltage; determining anappropriate transmitter output level sufficient for transmitting databetween the mobile unit and a base station; determining transmittersupply voltage needed to transmit at the appropriate transmitter outputlevel; converting the battery voltage to the needed supply voltage whenthe battery voltage is not substantially the same as the needed supplyvoltage by providing an oscillating pulse to activate a voltageconverter using a pulse generator; and disabling the converting stepwhen the battery voltage is substantially the same as the needed supplyvoltage by providing a constant voltage to deactivate the voltageconverter using the pulse generator.